Using Javascript .sort function to sort strings containing numbers

Question

I have following Array of Objects containing strings:

[{"code_name":"SNOMED","code_system_id":"1234"},{"code_name":"2BPRECISE","code_system_id":"4567"},
{"code_name":"UMLS","code_system_id":"7894"}]

The strings need to be sorted in alphabetical order, the following function was used:

.sort((a, b) => a.code_name - b.code_name)

Expectation:

[{"code_name":"SNOMED","code_system_id":"1234"},{"code_name":"UMLS","code_system_id":"7894"},
{"code_name":"2BPRECISE","code_system_id":"4567"}]
OR
[{"code_name":"2BPRECISE","code_system_id":"4567"},{"code_name":"SNOMED","code_system_id":"1234"},{"code_name":"UMLS","code_system_id":"7894"}]

Actual Results:

[{"code_name":"SNOMED","code_system_id":"1234"},{"code_name":"2BPRECISE","code_system_id":"4567"},
{"code_name":"UMLS","code_system_id":"7894"}]

My understanding is that the .sort function sorts based on utf-16 although unclear how then to get my expected result. How can I get my expected result (either one)?

The subtraction operator works with numbers, not alpha strings. — Pointy, Apr 26 '20 at 13:09
```.sort((a, b) => a.code_name > b.code_name ? 1 : -1)```. Use this. — Sajeeb Ahamed, Apr 26 '20 at 13:10
@SajeebAhamed that is incorrect; it does not account for two equal strings. — Pointy, Apr 26 '20 at 13:10
@Pointy aren't there performance issues with this? https://stackoverflow.com/questions/55695675/localecompare-vs-sort-for-alphabetically-sorting — Michael, Apr 26 '20 at 15:22
@Michael if you're sorting a list of 200,000 objects, maybe. — Pointy, Apr 26 '20 at 15:27
@Michael also note that the root question with the performance issue is 7 years old, right about the time that `.localeCompare()` became available. — Pointy, Apr 26 '20 at 15:28

score 1 · Answer 1 · answered Apr 26 '20 at 13:21

sort accepts the comparator function for an ordered pair of elements. eg:

for elements e1,e2 :

if e1 > e2 compartor = 1 
if e1 < e2 compartor = -1 
if e1 = e2 compartor = 0

cor your case :

const comparator = (e1,e2) => {
    if(e1.code_name>e2.code_name)return 1
    if(e1.code_name<e2.code_name)return -1
    if(e1.code_name>e2.code_name)return 0
}

test forward :

let input = [{"code_name":"SNOMED","code_system_id":"1234"},{"code_name":"2BPRECISE","code_system_id":"4567"},
{"code_name":"UMLS","code_system_id":"7894"}]

const comparator = (e1,e2) => {
    if(e1.code_name>e2.code_name)return 1
    if(e1.code_name<e2.code_name)return -1
    if(e1.code_name>e2.code_name)return 0
}

console.log(input.sort(comparator))

test revers :

let input = [{"code_name":"SNOMED","code_system_id":"1234"},{"code_name":"2BPRECISE","code_system_id":"4567"},
{"code_name":"UMLS","code_system_id":"7894"}]

const comparator = (e1,e2) => {
    if(e1.code_name>e2.code_name)return -1
    if(e1.code_name<e2.code_name)return 1
    if(e1.code_name>e2.code_name)return 0
}

console.log(input.sort(comparator))

You don't need the third `if`; if one is not greater than the other, the only other possibility is that they're equal. — Pointy, Apr 26 '20 at 14:09
yeah, it can be removed. I post this just to explain how the comparator works. — Nilanka Manoj, Apr 26 '20 at 14:11

score 1 · Answer 2 · answered Apr 26 '20 at 13:31

You can try this:

const data = [{"code_name":"SNOMED","code_system_id":"1234"},{"code_name":"2BPRECISE","code_system_id":"4567"},
{"code_name":"UMLS","code_system_id":"7894"},
{"code_name":"SNOMED","code_system_id":"1234"}];


const compare = (dirn) => {
 if (dirn === 'asc') {
     return (a, b) => {
  if (a.code_name === b.code_name) return 0;
  return a.code_name > b.code_name ? 1 : -1;
     }
 } else if (dirn === 'desc') {
     return (a, b) => {
  if (a.code_name === b.code_name) return 0;
  return a.code_name > b.code_name ? -1 : 1;
     }
 }
}

console.log('asc', data.sort(compare('asc')));
console.log('desc', data.sort(compare('desc')));

.as-console-wrapper {min-height: 100%!important; top: 0;}

Using Javascript .sort function to sort strings containing numbers

2 Answers2